What are Intersections?

An intersection is defined as the crossing of two pre-defined VOR radials, or in some *extremely* rare cases (one airway in South Carolina, and a few in Alaska) using an NDB bearing. In most cases, intersections are placed along Victor Airways and often are also the intersection of two airways. They're also used for instrument approaches, or sometimes merely as fixes used for enroute or holding. You can locate the intersection a couple of ways.

If you have 2 VORs then you simply tune one into NAV1 and twist the OBS to the appropriate radial, and do the same on NAV2 for the second intersecting radial. When both CDIs are centered, you're at the intersection. You can also do this with one VOR, which is all that is legally required, but then you have to constantly switch frequencies and twist the OBS to update your position.

Navigating to the intersection usually involves tracking one of the radials (flying along it). You then can set NAV2 (or again, swap back and forth) to the corresponding VOR radial. When the CDI swings from one side to the other, you've passed the intersection.

The Victor (low altitude) airways are used below FL180, and the Jet (high altitude) routes are used above that. All are defined by VORs, but often the VORs used to define the J- routes are not able to be received at lower altitudes for the entire length of the airway.

In real life IFR, ATC assigns altitudes, which may not always be the initial altitude you filed for. And they may (usually do) change your altitude assignment from time to time while enroute. In real life VFR, you choose your own altitudes and, when more than 3,000 ft. AGL, you are expected to follow the East/West rule.

In FS IFR, you pick your one and only altitude (FS9 and FSX have improved this situation, though) when filling out the flight plan, and ATC will always assign you that altitude. In FS VFR, the most you can do with ATC outside a terminal area is VFR flight following, which works much as in real life, i.e. you choose your altitude, and should (if you want to follow real-world rules) go with the East/West rule.

In real life IFR, you can negotiate with ATC for altitude changes (and routing changes, for that matter) at any time. In FS, you're stuck with the initial choice (FS9 and FSX have improved this situation, though).

And, in FS IFR, it seems that ATC always starts vectoring you (sometimes weirdly) when you are around 60-70 NM from your destination rarely, if ever, paying attention to the surrounding terrain. In Colorado Springs (KCOS), for example, my vectors put me over the foothills west of town just barely (300-500 ft) above some of the terrain. I had the feeling that if the wind had been different, I'd have actually been vectored into the mountains. There don't seem to be minimum vectoring altitudes built in to FS (ATC MUST follow these, in real life, or you'd have lots of bent metal).

A note about intersections: In real life, if you have an IFR certified GPS, you can often legally use the GPS to find intersections, rather than the VORs. There's more to it than that, but I won't go into it here.

See also the Wikipedia entry intersection (aviation).

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